[fitswcs] VO standard for JPEG with WCS

[Doug Mink]

William Pence wrote:
> FYI, there was a brief email exchange on the VO email lists 
> (apps at ivoa.net and dal at ivao.net) concerning encoding WCS information in 
> JPEG images.  Copies of the current thread of 3 messages are shown 
> below.  If you are interested in this topic, you can subscribe to the 
> email lists at http://www.ivoa.net/forum/

We had a need to put WCS on colored images in JPEG or GIF formats, so
I added an under-documented feature to the WCSTools package to check for
a FITS header appended to such a file and extract WCS information from
it.  This is pretty simple, though I'm not sure what JPEG readers will
do with data past the end of the image.  I just used

imhead -f wcsfile.fits >>wcsfile.jpeg

and then imsize, xy2sky, sky2xy, etc. can read WCS parameters from
the JPEG image.

-Doug Mink